This invention relates generally to systems and methods employing a charge coupled device (CCD) and particularly to such a system and method for inspecting or modifying images projected onto the CCD.
Charge coupled devices are finding use in a wide range of equipment requiring image sensing, such as inspecting or modifying elements by examining the images cast by the elements into the CCD. CCDs are used in conjunction with an optical lensing system which focuses the light from the object being investigated onto the CCD. Varying amounts of light on the individual pixels, or light sensitive material locations, within the CCD array charge the pixels to different levels proportional to the incident light. The optical information from the object is, therefore, available in analog form across the pixels of the CCD array. The analog information is shifted out of the CCD and converted into digital form and stored in a digital memory where the various characteristics of the object can be investigated by the proper manipulation of the digital information. The individual pixels within a CCD array typically are closely spaced and are arranged horizontally in rows and vertically in columns so that a given CCD imaging device will provide a fixed number of pixels of information. As an example, the SID52501 CCD presently available from RCA Corporation has 320 vertical columns of pixels and 512 horizontal rows of pixels. Accordingly, the information is read out from the CCD and stored in 320 vertical columns and 512 horizontal rows.
One use for CCDs is that of inspecting objects by examining the images cast by the objects onto the CCD. As an example, the object being inspected can be a production CCD. An optimum CCD, or a programmable digital processor, is used to provide a reference field. The data from the reference are stored in a reference frame store. A production CCD is then imaged and the data received therefrom are compared, pixel by pixel, to the reference field data from the optimum CCD or the digital processor. The exact locations of faults in the production CCD are thus identified. Alternatively, the initial image can be provided by a high resolution CRT whereby the image can be varied pixel by pixel. The data representative of a desired image are placed into the reference store and compared with the data received from an actual image on the CRT screen. The difference between the two images is then used to change the CRT image on a pixel by pixel basis until the data from the projected image matches the data representative of the reference image. The projected image can then be photographed to produce a complex transmission characteristic which otherwise is difficult, or impossible, to produce.
The instant invention utilizes the advantages of a CCD by the provision of a CCD based image inspection system and method wherein the image cast by an object, such as another CCD, is compared with a reference image to identify the locations of faults, or to modify the image.